From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335

Fall 1996, No. 1


Recent years have reminded us of how unpredictable and uncooperative spring weather can be. Field operations for which timeliness is critical...tillage, herbicide application, and planting...are often complicated and delayed by wet fields in the spring. That’s why appropriate fall fertilization should be considered as a means of reducing the spring work load.

For fall fertilization to be appropriate, it should be based on a valid set of soil tests. The first step in planning next year’s fertility program is soil testing. Fall is an excellent time for soil sampling. Good post-harvest soil conditions typical of the fall season allow better control of sampling depth. Fall sampling avoids the rush experienced by soil testing labs in the spring and the ensuing delays in receiving test results. Furthermore, research in several states has indicated that fall samples are just as accurate as samples taken at other times.

Appropriate fall application of phosphorus, potassium, and lime is agronomically sound.
What about nitrogen in the fall? The effectiveness of fall applied nitrogen is region and soil-specific. Fall application of nitrogen is not recommended in parts of the eastern Corn Belt or on sandy soils. In the western Corn Belt, nitrogen can usually be applied in the ammonium form after soil temperatures remain below 50°F all winter. However, local best management practices should be checked before nitrogen is applied.

Appropriate fall fertilization is environmentally acceptable. “Appropriate” in this context means that nitrogen best management practices are followed as discussed above; phosphorus and potassium are not applied to soils prone to erosion over the winter; and potassium is not applied to soils with cation exchange capacities less than six. An environmental advantage for fall application is a reduced chance of phosphorus loss in runoff during intense rainfalls soon after application. Since the major run-off events occur in the spring in much of the Corn Belt, fall application offers more time for soil-fertilizer reaction before the first runoff event is likely.

Appropriate fall fertilization is economically wise. Fall application takes advantage of the historical trend of lower fall fertilizer prices and special dealer incentive programs. It is part of an intensive approach to crop production that plans for and produces higher and more profitable yields.

- PEF -
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